The purpose of a router is to connect nodes across an Internetwork, regardless of the Physical layer and the Data Link layer protocol that is used. Routers are aware of the Network layer protocol, and not aware of the type of medium or frame that is being used. Routers operate on the OSI Model's Network layer. Physical layer devices are: NIC, Transcievers, Repeaters, Hubs, MAU, etc. Data Link layer Devices: Bridges, Switches, etc. Network layer devices: Routers, Brouters, Layer 3 switches Gateways are used to connect dissimilar networks, they function at a high end typically Network layer and above of the OSI model.